The long-term goals of this research are to quantify patient-specific changes in neuromuscular control in order to optimize treatment planning and improve mobility for individuals with cerebral palsy (CP). As a first step, the aims of this proposl are to evaluate neuromuscular control before and after one of the most common treatments for individuals with CP, orthopaedic surgery. We will evaluate if patient-specific measures of neuromuscular control, based upon the framework of muscle synergies, can predict improvements in walking ability after surgery. Further, we will determine whether neuromuscular control changes after surgery and if these changes contribute to improvements in movement. To achieve these goals we will implement and test new tools to quantify neuromuscular control which integrate clinical gait analysis and two computational techniques: synergy analysis and dynamic musculoskeletal simulation. Our prior research has demonstrated that individuals with CP use fewer synergies during gait than unimpaired individuals and that synergies are associated with changes in walking ability after a variety of treatments. In Aim 1, we will prospectively evaluate if synergies predict outcomes after orthopaedic surgery. In Aim 2, we will evaluate the adaptability of synergies by evaluating whether synergies change after orthopaedic surgery. In Aim 3 we will use musculoskeletal simulation to evaluate how altered synergies impact muscle recruitment, impaired movement, and energy costs of walking for three of the most common pathologic gait patterns in CP: crouch gait, stiff-knee gait, and equinus gait. Musculoskeletal simulation provides a unique tool to probe patient-specific changes in neuromuscular control because we can specify and evaluate different control strategies and impairments in silico. For example, we can use a patient's experimentally measured kinematics and kinetics from clinical gait analysis to simulate their specific gait pattern and examine the impact of different control strategies. We will use a new algorithm we developed in OpenSim, an open-source platform for musculoskeletal modeling, to create simulations with synergy-based control. The outcomes of this research will quantify changes in neuromuscular control in CP and evaluate the clinical utility of synergy analysis. This research will provide the foundation to use measures of altered neuromuscular control to inform treatment planning, develop alternative treatments, and improve mobility in CP and other neurologic disorders.